MODEL GAME THEORY & SAPPHONS · FOLDED STARS · POLYGONS · under KEEPER ERIS

Star Polygons {n/k} · Schläfli

Join every k-th of n points on a circle and you draw the star polygon {n/k}. If gcd(n, k) = 1 it is one stroke; otherwise it falls apart into a compound, like the hexagram {6/2} = two triangles. The I-13 VM computes the gcd and every vertex with its own sine series.

Dave (t252): "i love that set up can you build some pages looking into game theory and those sappons you just built, see if you can build some folded stars and stuff"

Dave’s I-13 engine on this page

booting I-13 v0.3…

LIT What the VM computes here: The VM computes gcd(n, k) by Euclid using only subtraction (it has no modulo), and every vertex (cos, sin) with its own range-reduced sine Taylor series. It also gives the tip angle, edge, inner radius, and the gcd of n with every k. The canvas is drawn from the VM’s coordinates.

LIT Schläfli symbol {n/k} (Poinsot 1809 studied them; the notation is Schläfli’s): n points equally spaced on a circle, each joined to the one k places on. The tip angle is 180°(1 − 2k/n): 36° for the pentagram {5/2}. k is the density, how many times the outline winds around the centre.

LIT If d = gcd(n, k) > 1 the figure is a compound of d copies of {n/d, k/d}: {6/2} = 2{3}, the Star of David; {8/2} = 2{4}, the octagram compound. For n points there are φ(n)/2 − 1 single-stroke regular stars (φ = Euler’s totient): 2 for n = 7, 1 for n = 8, 1 for n = 12.

LIT Edge length 2 sin(πk/n) on the unit circle; the inner (valley) radius of the outline is cos(πk/n)/cos(π(k − 1)/n), which is how every folded star in this batch is built.

MODEL Game tie-in: in a cyclic game where move i beats move i + k (mod n), the best-response arrows trace the star {n/k}, and the only equilibrium is to play all n moves uniformly. Rock–paper–scissors is the {3/1} case. The agents learn the {7/3} game.

Lab MODEL interactive, computed on the I-13 VM

n · k

Sources (browsed Oct 2026)

  1. MathWorld: Star polygon
  2. Stellating and facetting: a brief history (Poinsot 1809)
  3. Star polygon (overview, compounds)

MODEL Two agents, as Dave set for every world: STAR A and STAR B play the cyclic {7/3} game (each move beats the one 3 steps on, MODEL) over and over by regret matching (Hart & Mas-Colell 2000), each shifting toward the moves it regrets not having played. Their score is 1 − NashConv/2 of their empirical average play (1 = an exact Nash equilibrium), and the I-13 VM re-computes NashConv from the raw averages every time the score improves. The centrepiece is a folded star {7/3} whose fold rises with the score. Three.js r160 from a pinned CDN, devicePixelRatio capped at 2. Drag to orbit, scroll to zoom.

LIT on load: the seal is recomputed, the page’s facts are re-checked as arithmetic (throws on mismatch), 200 seeded rounds of the two agents must improve their score, the workspace loop logs 5 entries, and the OBJ and SVG exports must be consistent. Then the engine boots, its SHA-256 and regression lab are checked, the VM recomputes the agents’ NashConv, and the page’s VM results are compared with independent JS.

Gallery of kept moments (WebGL snapshots):

Workspace improvement loop: instructions for agents MODEL

  1. Measure: every 40 rounds, record NashConv of the average play, the score, the rounds since the last improvement and whether regret-matching+ is on.
  2. Try next: after a 40-round plateau, switch both agents to regret-matching+; if still stuck, halve the exploration ε; if still stuck, forget half the old history. While NashConv falls, keep course (ε × 0.9); if it rises, explore more (ε × 1.25).
  3. Log back: append {entry, round, measured, tried, ε} to the workspace log (in the JSON export and the list below), and have the I-13 VM recompute NashConv.
  4. Repeat, forever: never stop improving. Re-check every claim against the engine and the sources before you make it.

Live workspace log:

    Shared board MODEL STAR A ↔ STAR B

      Background art: MODEL a generative field seeded from this page’s seal.

      proving…

      Seal sha256(name|slug|blurb): c0f8a1d2a26a9b65572da15c629439afb18fbf2e88cd64d9288aaddcaaf22bf7

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